Testing device.



UNITE STATES FLATENT ALVARADO L. R. ELLIS, OF LYNN, MASSACHUSETTS, ASSIGNOR TO GEN- ERAL ELECTRIC COMPANY, CORPORATION OF NEW YORK.

TESTING DEVICE.

, To @ZZ whom it may concern:

Beit known that I, ALVARADO L. R. Erme.' a citizen of the United States, residing at Lynn,` county of Essex, State of massachusetts, have invented certain new and useful Improvements in Testing Devices, of which the following is a specification.

This invention re ates to testing devices, and particularly to devices for testing magnets.

The object of the invention is to provide a device for testing magnets which is unaiiected by temperature changes, in which errors due to air-currents are prevented, which measures the eiective strength of the magnets rather than the total number of lines of force set up thereby, with which errors due to friction or faulty observation of the o er ator are reduced to a minumum, and w lich permits of testing magnets with great accuracy and rapidity.

Permanent magnets are largely employed in electrical measuring instruments to retard the movements of the movable element of the instrument ,or tov afford operating torque. Obviously it is important that for all such uses, and "particularly for use in integrating meters of the motor type, the strength of the magnet should be known. These magnets are ordinarily used coperating with a plate or disk of conducting material mounted on the Kshaft of the movable element of, the in? strument to rotate in the field of the magnet, sothat the movements of the movable ele- `ment are retarded by the generation of eddycurrents in this disk or plate. For this reason the measurement ot the strength ofthe magnet should be a measurement of its drag effect rather than a measurement ofthe total number of lines of force' set up by the magnet, since the drag effect of two magnetshaving the same number of lines of force may difi'er owing to differences in the distribution of the lines with respect to the pole-faces. I therefore provide means for measuring a magnet in just the way it is used in a measuring instrument-that is, by measuring the retardation of a plate or disk moving m its field.

In carrying out my invention employ two similar motor. mechanisms having their shafts arranged to actuate a diHerential gear which serves to give an indication of the relative speeds of the 'o shafts. The shaft of Specification of Letters Patent.

Application nea coats 9.411905. sain No. 2811.014.

Patented Nov. 27, 1906. I

yneof -the motors .carries ar plate or disk of conducting material arranged to rotate in theiield of a magnet of known strength,

which is used as a standard of comparison.

The shaft of the other motor carries a similar plate or disk, and to this the magnets to be tested are applied in the same manner as the standard magnet is applied to the disk ofthe .first motor. If a magnet to be'tested is applied to the disk ofthe second motor mechanism and the two similar motor mechanisms are run under exactly the same conditions, their speeds will be inversely proportional to the drag effects of the two magnets and `their cooperating disks. In order that the ma nets may be tested rapidly, I employ electric motors to drive the shafts carrying the disks of conducting material and provide means' for varying the current suppllied to the motor driving the disk with whic the magnets to be tested cooperate.` Then by varying the' current supplled t'o-this motor until the two shafts are rotatin at the saines eed, as in d icated by the di erential gear, t e Ystrength of the magnet to be tested relative to"`the` standard magnet may be obtained from the.

ratio of the energy consumed by the two-electric motors. I

The novel features of my invention be definitely indicated in the claims appended@ hereto.

of operationof my improved testing device will beI better understood by reference to the following description, taken in jzon'nection with the accompanyin drawings, which show the preferred embodiment ofthe invention, and 1n which- Figure l is a sectional elevation of my improved magnet-testing device. Fig. 2 is a diagram of theelectrical connections, and Fig. 3 is a perspectiveview of the support for the magnets to be tested.

Referring to the drawings,f1` indicates anisms, one above the other.

,51, casing which ineloses the operating parts, -within which are mounted. two motor, mechv These motors are` preferably of the same size andfare simif 5 The details of construction and the method IOC lar in all their constants and characteristics.

In the drawings are shown two smal electric motors such as .are employed in integrating electric meters. These are induction metermotors ofstandard construction, each consisting of a magnetic structure 2, providedwith suitable poles, on which are mounted series A coils 3 a shunt-coil 4, and a short-circuited coil 5 for lagging the flux due tothe potential coil 4 and a shaft 6,1nountedfor rotation in suitable bearings and carrying a which 1s arranged to rotate between the poles on which the series and shunt coils 3 and 4 are mounted. 1Rotation ot' the moving eley ment ci' Athe upper meter is retarded by a peri e manent magnet S, mounted en the trame 9 in such a position that-'the disk 7, et conducting material, carried vby shaft 6, rotates in its eld. The magnet 8 is a standard to which other magnets are to be compared. 0n the shaft j6 is mounted a gear il), meshing with a gear 1l, which is'loose on a shaft 12. This shaft is mounted for rotation in bearings formed one in the frame 13 ot the lower motor mechanism and the other in a spring-arm la, whose inner end is secured to the trame' 9 and whose outer end may be moved against the tension of the spring; so as to release shaft 12 to permit of removing the shaft and the arts of the differential gear which are carried thereby. A gear l5, similar to th gear 11, is loose on shalt 12 at its lower end and meshes with a gear 1-6, carried by the shaft 6 of the lowerinotor mechanism. The gears 11 and 15 have teeth Jformed on the adjacent sides thereoi'fwith which meshes a gear 18, loose on a shaft 19, which is secured to a sleeve 20, mounted on shaft i2. Extending radially from sleeve are a plurality of arms 21, which at, their outerends rcarry a ring 22,having niarks thereon, as shown in Fig. 1. An indicator 23, extending down from the ltrarne 9 over the ring 22 enables the operator to accurately read the movements o.

extends throughan opening in the casing i' and into a slot in an auxiliary casing 24, of

non-magnetic material,l secured to the main 'casing 1 andforming an inclosure, having -very thin Walls above and below the portion of the disk 7 extending beyond the casing 1,. The auxiliary casing 24 is (preferably a casting of brass heavily ribbe to y give it greater strength and provided with ledges on which rest thin sheet-metal plates 25, which form the top and bottom of the inclosure. The thickness of the inclosure is the same as the air-gap between the poles of a magnet to be tested. Below. the inclosure 24 is a support 26, mounted on the base of the casing 1 and arranged to be adjusted vertically by means et screws 27, projecting upwardly from the base of the casing l and nuts 28 on these screws positioning the support 26. The upper surface of support 26 is shaped so as to receive a magnet to betested and guide it as it is slid over the surface of the support into position, with its poles -one above and the other below the inclosure 24. Two pins 17 are .inountedin openings in the frame 13 of the dish armature 7,

esame lower motor mechanism and extend through openings in the auxiliary casing 24, and the ends or these pins are engaged by a magnet to be tested when the latter is being moved into position to limit the movement of the magnet and to insure 'accurate positioning of the magnet with respect to the disk 7. The pins 17 may be moved tothe desired position in the openings in frame 13 and-then locked in that posi ,can by set-screws 17. lf desire-d, a wiper 2Q may be mounted on the forward end oi the inclosure 2e to brush oli the poles ot' the magnets they are slidinto position on the inclosure, and thus remove all able resistance 33 of greater ohmic value than the resistance 32 across the lines. the manutacture ci electric measuring instruments it is common to use permanent magnets arranged in pairs and held in suitu able clamps, and the testing vdevice illustra-ted in the drawings is arranged for testing such pairs ci magnets, though it will be understood that the construction can be readily changed to accommodate single magnets and magnets of various shapes. With the support 26 in the proper position of vertical adjustment a pair of magnets 34 to be tested held in a clamp 35 'are placed upon the support 25 at its forward `end and are moved along over the support to slidethern into position, with one poe of each magnet above and the other below the inclosure 2e,

Auntil ini-ther movement is arrested by the magnets engaging the adjustable stops i7. ln this position the linx of the magnets 34 intersects the disk 7 of the lower motor mechanism'and retards the rotation' of 'the moving element thereof. lf the olimic value ofthe resistance 33 cut into the circuit'v oi" the series co'ils 3 ot the lower motor is the same as thatot the resistance 32, so that the' coils of one motor receive the same amount of current asthe corresponding coils of the l other, the two motors will develop the same amount of torque, since they are similar in every respect, have similar constants and characteristics, and are connected in the same circuit. This will be true regardless of changes of voltage,frequency, and wave form of the lines 30 and 81, as such changes affect both motors alike. lf the standard magnets 8 and the magnets 34 to be tested are of the same strength, they will exert the same drag effects on the moving elements of the two motor mechanisms, which will therefore rotate at the same speed, and in this case the intermediate wheel 18 of the differenti al gear will not turn around shaft 12, though it wi ll of courserotate on its shaft 19. The ring 22, therefore, will not be moved, and the operator by looking through the glass 37 in the casing 1 will know that the two shafts are rotating at the same speed from the fact that the ring 22 does not move relatively to the indicator 23. If the magnets 34 to be tested are of a different strength from that of the standard magnets 8, the shafts of the two ential gear and the case the strength of the magnets to be tested .motors will rotate at diferent speeds and the intermediate wheel 18 of the differential gear will not only turn upon its own shaft 19, but will move around the shaft 12, and thus cause ring 22 to move relativel to the indicator 23. If the magnets to e tested are of greater strength than the standard magnets, thering will move in one direction, and if of less strength it will move in the opposite direction. i.

From the rate and direction of movement of ring 22 relative to indicator 23 a measur'ement of the strength of the magnets to be tested relative to the standard magnets can be obtained. However, in order that the measurements may be more rapidly obtained I provide means for adjusting the current supplied to one of the motors and obtain the measurements by a com a-rison of the torques of the two motors. T iis is done in the following manner: The operator on noticing the movement of the ring 22 moves the arm 38, governing the adjustable resistance 33, to vary the current flowing through the series coils 3 of the lower motor, thus changing the speed of rotation of the movable element of the lower motor until the moving elements of the two motors are rotating at the same s eed again, which fact will be indicated by t 1e ring 22 of the difierindicator 23. In this bears to the strength of the standard magnets the -same relation as the energy expressed in watts consumed in the actuating-coils of the lower motor bears to that consumed in the coils of the upper motor. However, it is unnecessary to measure the watts consumed, as the two motors are connected in the same circuit, and fixed and adjustable resistances 32 and 33 of known values are included in the circuits of the two series coils 3 and 3', respectively, and the strength of the magnets to be tested relatively to that of the standard magnets may be found from the values of the fixed known resistance 32 and the portion of the adjustable resistance 33 cut into circuit to bring the two motors to the same speed. To further simplify the operation of making @uch changes, and

the measurements, the adjustable resistance 33 may be calibrated, so that the measurement is obtained immediately from the position of the rheostat-arm 38 of the adjustable resistance when the ring 22 is brought to rest. In F ig. 2 I show the rheostat marked olf to read in per cent. of strength of the magnets to be tested relatively to the standard magnets, which are taken as one hundred per cent. 7 5

It will be seen that the instrument is independent of changes in the voltage, frequency, and wave form of the actuating-current, that since changes of temperature effect both motor mechanisms alike it is independent of that since all the parts are mclosed within the casing they are not affected by air-currents. A slight movement of the ring 22 relatively to the indicator' 23 is readily detected, and therefore the arm 38 may be quickly brought to the proper position to give equal rotation of the movable elements of the two motor mechansisms. This, together with the fact that the tested can be quickly and accurately moved into position and need no further adjustment, makes it possible to work very rapidly.

Although the device I have illustrated and described herein is particularly useful in testing the strength of permanent magnets, I do not wish to be understood as limited to that use, as the novel combinations of parts set forth in the appended claims may be used for other purposes. Also various modifications of the construction of the magnet-testing device as illustrated in the drawings can be made without departing Vfrom the spirit of my invention, and all such modifications I aim to cover by the terms ofthe claims appended hereto.

What I claim as new, and desire to secure by Letters Patent of the United States, is*` -1. A testing device com. rising a standard magnet, and means for in icating the eHective strength of another magnet 1n comparison with that of the standard magnet.

2. A testing device comprising a standard, magnet, a motor, a plate of conducting ma' terial driven by said motor arranged to revolve in the 4field of 'said magnet, a second motor, a plate driven thereby, and means for comparing the retarding strength of the standard magnet and that of a magnet so placed that the second plate cuts its magnetic field. Y

3. The combination of two motors, means forindieating their relative s eeds, a late of conducting material driven y one o saidk motors, and means for facilitating the application of a magnet to said lateso that the plate cuts the flux of its field).

4. The combinationof two motors, means for indicating their relative speeds, a plate of conducting material driven by one of said motors, and a supporting device for holding a magnets to be 'ICO IIO

magnet in osition for said plate to cut the field thereo 5. The combination of tWo motors, means for, indicating their relative speeds, a plate of conducting material driven by one of said Amotors, a support for holding a magnet in position for said plate to cut the tield thereof, and means permitting adjustment of the support relative to the plate.

6. The combination of two motors, means for indicating the relative speeds thereof, a plate oi conducting vmaterial driven by one of said motors, and a casing inclosing the arts sha ed to ermit a 'i ilvinff a maffnet to- P P ll s s the plate so that the latter cuts its iield.

7. The combination of two motors, means for'indicating their relative speeds, a plate of conducting material 'driven by one of said motors, and thin sheets of non-magnetic material mounted above and below said plate.

S. The combination ci two motors, means for indicating their relative speeds, a plate of conducting material driven by one of said motors, and a casing inclosing the parts incliiding thin sheets of non-magnetic material mounted above and beloiiT said plate. f

9. The combination ot tivo iiiotcrs, means for indicating their relative speeds, a plateoiiconducting material driveniby one ol said motors, a supporting device over which a magnet may be slid to more it to a position in which said plate cuts its lield, and an ad.- jiistable stop to limit the position of the inagnet.

i0. The combination of tivo motors, means for indicating therelative speeds thereof, a

`,plate of conducting material driven oy one therefrom, and means for adjusting the relaci said motors, a supporting device for holding a magnet in a deiinite relation tosaid plate permitting magnets to be rapidly mountedin position thereon and Withdrawn tion which the magnets are held.

11. The combination of tivo motors, means for indicating the' relative speeds thereof, a l

plate of conducting material driven by one of said motors, a magnet Whose iield is cut by said late, a second 'plate of conducting materialdriven by the other motor,- and means tor facilitating the application of magnets to said plate so that the plate .cuts the magnetic iield.

. 12. The combination of tivo motors a dif.

erential gear actuated by the shaits thereof, an indicator controlled by said `gear, a plate of conducting material driven by the shaft of.

oiie of said motors, and means for facilitating the application ot magnets to said plate so that the plate cuts the-magnetic field.

13. The combination of two motors, a differential gear actuated by the sliaf ts thereof, an indicator controlled bythe intermediate of' said 0fear, a plate of conducting lmaterial driven one of said motors, al magnet whose field is cut by said plate, a second plate lof conducting material driven Aby the i other motor, and means for facilitating the a plicaticn of the magnets to said plate so t at the plate cuts the magnetic iield.

le. The combination of two electricmotors, means for indicating their relative speeds, disks of conducting ymaterial'driven by the shafts thereof, a magnet Whose eld r is cutby the disk of one of the motors, and means for holding a magnet in a deinite relation to the disk oi the other motor.

, i5. The combination of an electric circuit,v

two electric-motors connected therein, means for indicating the relative speeds of said motors, a resistance in circuit With one motor, and an adjustable resistance in series with the o ther' motor.

16, The combination of an electric circuit, two electric motors connected therein, a differential gear actuated by the shafts of said motors, indicating devices controlled by said gear, a resistance in circuit with one of said motors, and an adjustable resistance in circuit With Athe other of said motors.

17. "The combination ot an electric circuit, Wo electric motors connected therein, means vfor indicating the relative speeds of said mo-v tors, an adjustable resistance in circuit with one of said motors, a plate of conducting material driven by said motor, and means for facilitating applying magnets to said plate so that the plate .cuts the magnetic field.

i8. The combination of an electric circuit, tivo electric motors connected therein, means for indicating the relative speeds of said motors, a resistance in circuit- With one of Said motors, a disk of conducting materialdriven by said motor, a magnet in Whose iield the 'disk moves, an adjustable'resistancc cir-V cuit Wit'h the other motor, a disk of conducting material driven by said motor, and

means for facilitating a plying magnets- 'to' said disk so ,that the dis vcuts the magnetic fields thereof.

i9. A magnet-testing device comprising a motor mechanism,.a plate of conducting ma- ,terial driven thereby, and a casing inclosing the motor mechanism and plate shaped to permit applying a magnet to the plate so 4that the latter cuts its iiel 20. A magnet-testing device comprising a f 22. A magnet-testing device comprising a IOO plate to cut the motor mechanism, a plate of conducting material driven thereby, a casing'inclosing the motor mechanism and plate including thin Sheets of non-magnetic mate1ial-above and below the plate, a support for holding a 1nagnet in position for said plate to cut'the llux of its field, and means for adjusting said support relative to said plate.

23. A magnet-testing device comprising a motor mechanism, means for adjusting the speed thereof, a plate of conducting mate-rialA driven by the motor, a support on which a magnet is adapted to be rested'to hold the magnet in position for the plate to Vout its field, and means permitting adjustment of the support toward and away from the plate. 24. A magnet-testing device comprising a motor mechanism, a plate of conducting material driven thereby, and a su porting device over which a magnet is aditpted to be slid to move it to and away from a position in which the plate ents the field of the magnet. 25. A magnet-testing device comprising motor mechanism, a plate of conducting material driven thereby, a. supporting device over which a magnet is adapted to be slid to move it to and away from a position in which the plate cuts the iield of the magnet, and an adjustable stop to limit the movement ofthe magnet into position. A

26. A magnet-testing device comprising a motor mechanism, means for `adjusting the speed thereof, a plete of conducting material driven by the mechanism, and a supporting device for holding a magnet in a definite relation to said plate with the plate cutting the field thereof andl permitting magnetsto be readily mounted in' position thereon and Withdrawn therefrom.

27. A magnet-testing device comprising an'electric motor, means 'for adjusting the supply of current thereto, a plate of conducty ing material driven by the motor, and a supporting device for holding a magnet in a deiinite relation to said plate with the plate eutting the field thereof and permitting magnets to 'ne readily mounted in position thereon and withdrawntherefrom.

28. A magnet-testing device comprising a motor mechanism, a plate of conducting inaterial driven thereby, and an inclosure for said plate shaped to permit a magnet to be moved to a position in which the poles thereof embrace the inclosure and ythe/platt; of the conducting material therein.

In witness whereof l, have hereunto set my hand this th day of October, 1905.

ALVARADO L. R.' ELLIS.

Witnesses JonN A. MollANUs, .HENRY O. WESTENDARP; 

